Velocity-based training affects function, strength, and power in persons with Parkinson’s disease.
Background Velocity-based training (VBT) is a unique new resistance-training technique, typically used by high-level athletes, which uses changes in velocity rather than load to dictate progressions. No study has examined the effects of VBT on performance in persons with Parkinson’s Disease (PD). Objective To compare the effects of 10% and 30% velocity threshold protocols on changes in functional performance, strength, and power in persons with PD following 12 weeks of supervised VBT, three days per week. Methods Participants were recruited from a university population and from individuals residing in surrounding neighborhoods using flyers, and from an existing phone list of persons interested in participation. Data collected before and after training included the 6-m walk test at habitual and maximal gait speed, the 5 time sit-to-stand test (5xSTS), 1 repetition maximum (1RM) testing for both the chest-press (CP) and leg-press (LP) exercise, and power testing for the CP and LP. Results Data from 16 subjects was collected for the analysis. Significant time effects were seen for the 6-m walk test at maximal speed, 5xSTS, 1RM for both CP and LP and peak power (PP) for the LP exercise. Secondary analyses revealed time effects for 5xSTS power, and the load at which PP was achieved for the CP exercise. A Wilcoxon signed rank test revealed no significant differences in the percentage of 1RM at which peak power was achieved for either condition. Conclusion Results indicate that VBT is an effective training modality for improving functional capability, strength, and power in persons with PD. All data was collected by graduate researchers at the University of Miami. All measures were taken as pre- and post-measurements before and after a velocity-based training intervention using resistance training in persons affected with Parkinson's Disease. Measures included functional strength, and power testing. Subjects came into the laboratory 3 times a week for 8 weeks to train under the supervision of undergraduate and graduate research assistants using computerized pneumatic resistance training machines (HUR Inc, Park Ridge, IL, USA). The “VelCode” column represents the two different conditions used to run the repeated measures. All subjects used velocity-based training, however the groups utilized two different deficits in order to train. The load-based group utilized a 30% deficit in velocity to determine progression, and the velocity-based group utilized a 10% deficit. All variables are listed with either the suffix “Pre” or “Post” to distinguish the two different time points used in the repeated measures. Missing data is due to injury, refusal to complete a test at maximal effort, or absence of subjects from testing.
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Testing Functional Testing: The 6-m walk tests at habitual and maximal speeds were performed using electronic timing gates (SpeedTrap, Brower Timing Systems, Draper UT, USA) to evaluate subjects’ mobility. Participants were instructed to stand on a starting line at the 0-m mark and the test started after the investigator’s “3,2,1, Go!” cue. Participants performed one practice trial and two actual trials for each test. The best of the two times for each test was recorded. The 5xSTS test was used as a measure of functional lower body strength in PD. Participants were given 1 practice trial, and 2 actual trials, each separated by a 1-minute rest. The lowest of these two trial times was recorded. Power outputs for the 5xSTS were computed also. One-Repetition Maximum Testing All strength and power tests were performed using two of the computerized pneumatic resistance machines, the chest press (CP) and leg press (LP). Chest-press 1-repetition maximum (CP-1RM) and leg-press 1-repetition maximum (LP-1RM) were assessed. Power Testing After the completion of strength testing on day 1, participants were provided with a 48-hr. recovery before returning for day 2 testing. On day 2, chest-press peak power (CP-PP) and leg press peak power (LP-PP) testing began with a warm-up of 10 repetitions at 30% 1RM using self-determined, controlled concentric and eccentric speeds. A second 5-repetition warm-up at the same load was then performed as rapidly as possible during the concentric contraction and at a controlled speed during the eccentric contraction. Peak muscle power was subsequently assessed at five relative intensities (40, 50, 60, 70, and 80% 1RM). The percentages were randomized to reduce any order effect. For each repetition, the concentric phase was performed as fast as possible, and the eccentric phase was performed over 1-2 seconds. Each repetition was verbally cued “3, 2, 1, Go!” Any repetition not performed properly was repeated after a 1-minute recovery. Statistical Analyses For 1RM, peak power and load at which peak power occurred, separate 2 (time) × 2 (deficit group) repeated-measures ANOVA were used to determine significant main effects and interactions. A Wilcoxon signed-rank test was utilized to determine changes in %1RMpp across the intervention period. Effect sizes for main effects and interactions during repeated measures ANOVA were computed as partial eta squared values (ηp2). An effect size for Wilcoxon signed-rank test was also calculated (r = Z/(sqrt(n)). The interpretation of the r values is .1 = small effect, .3 = medium effect, .5 = large effect. The significance level was set a priori at 0.05 for all analyses. All statistical analyses were performed with the IBM Statistical Package for the Social Sciences (SPSS) for Windows, version 28.0 (IBM Corp., Armonk, N.Y., USA), except for Cohens d, which was computed using a custom program written in Microsoft Excel (Microsoft Corp., Redmond, WA, USA).